1. Field of the Invention
The present invention relates to a keyboard having a plurality of key tops which are supported so as to permit relative movement with respect to a substrate.
2. Description of Related Art
In general, a keyboard is used as an input device in the field of an electronic apparatus such as a desk-top personal computer, and the like. A keyboard has a plurality of key tops having a contact type switch on the underside thereof. A key top is mounted with an axis portion slidably fitted into a housing having a guide hole, and can slide vertically up and down along the guide hole. When the key top is depressed against an elastic force of a resilient member such as a rubber sheet or a spring, a switch is depressed in interlock with the movement of the key top. The key top can be pulled upward to be removed from the housing, and then the rubber member can be replaced in order to customize the feeling of key touch.
An example of a conventional key top is disclosed in Japanese Patent Publication (Kokoku) No. H07-70273 (JP-07-70273-B1). On page 3, lines 22-44, JP-07-70273-B1 includes a description that “Housing 30 is generally comprised of housing portion 31, flange 32, leg portion 33, engaging claw 34, and bottom plate 35. Flange 32 extends laterally from the lower portion of both sides of housing portion 31, and as shown together in FIG. 3, its end is inclined a little downward from horizontal direction to provide abutting portion 32a for abutting to panel 11. Flange 32 has elasticity in a direction of Z-axis. In attached state, bottom plate 35 is provided at the height of base portion of flange 32 so as to form a gap to panel 11. Leg portion 33 and engaging claw 34 form a pair, and have same width dimension in the direction of Y-axis, and are respectively provided to project from both side ends of the lower surface of bottom plate 35. Engaging claw 34 has arm portion 34b and claw portion 34a at its lower end. Arm portion 34b is formed with thinner wall as compared to leg portion 33, and has elasticity in a direction of X-axis. Claw portion 34a has engaging surface 34c that engages with the lower surface of panel 11 in the state with housing 30 having been attached.”
Also, Japanese Patent Publication (Kokai) No. H05-166437 (JP-05-166437-A1) discloses another example of conventional keyboard. In paragraph 0011 to 0015, JP-05-166437-A1 includes a description that “Stem 3 which is disposed in housing 2 and moves vertically in housing 2, is integrally fitted to key top 1 that is operated by depression with a finger. At the position opposed to stem 3, rubber 5, membrane sheet 6, and leg portions 4 penetrating through mounting plate 8 are provided, and hooks 4a are formed at the distal ends of leg portions 4. Rubber 5, membrane sheet 6 having movable contact 7a and fixed contact 7b, and mounting plate 8 are respectively disposed at the lower portion of housing 2. Rubber 5 abuts to the lower face of stem 3 and deforms when a depressing force acts on key top 1, and with this deformation presses membrane sheet 6 to bring movable contact 7a into contact with fixed contact 7b. Rubber 5 functions, when the depressing force is released, so as to release the deformation, and restore key top 1 to the initial state. At the positions of rubber 5 corresponding to leg portions 4 of stem 3, holes 5a for inserting leg portions 4 are formed. At corresponding positions of membrane sheet 6 and mounting plate 8, holes 6a, 8a for inserting hooks 4a formed at the distal ends of leg portions 4 of stem 3 are respectively formed. Therefore, the size of holes 6a, 8a is larger than the size of holes 5a.”
In a keyboard having the construction in which individual pieces of housings are attached to a switch panel, wherein the keyboard has the structure such that housings are attached from the front side of the switch panel, a direction for removing a key top is same as a direction of pulling out a housing, and therefore, there is a problem that the housing may come out unintentionally together with the key top.